Was I right or in the wrong?

Am I in the wrong? One of my friends bought my little boy something for Christmas, which he already had & hasn't played with for a while. It kind of annoyed me a bit as I asked her what her son was into & what I could buy him, so that I didn't get him anything he didn't want, whereas she didn't ask me what my little boy liked & just went out & bought him something she thought he would like. She also bought him something else, which I thanked her for, but I didn't say anything about the toy he already had. I decided to put the duplicate present on our local free site as I thought someone else might like it for their little one. I didn't realise she was also on that site & she commented on it asking if we had got given 2 of the same thing. I explained to her that he got given it a while ago by my brother in law & that he didn't really play with it anymore. She then asked if she could have the one she gave him back so that she could give it to someone else. I said yes if she wanted to do that, then that was fine. The thing is, I was always taught that once you were given something, it was yours to do whatever you wanted with. Also, if she is just going to give it to someone else anyway, how is that any different from what I was doing? Should I have asked her before putting it on the group? Or maybe I just should have told her that he already had it but didn't play with it anymore, so she could have had the option to have it back? Opinions welcomed.